Telephone system



June 20, 1944. A, E. JOEL, JR

TELEPHONE SYSTEM Filed July so, 1943 4 sheets-sheet '1 IIHI- /N VE/v ron A. EZ JOEL 4 Tram/EY 2 7. n R. n l e 5 m RJ N 3, y 0L, m 2 .u .ME Y? m VJMA 4 WE@ AM. R M4 mw ,m0, y Jwm .u.d` EMd .Le Amm.. F 9 l 0.. 2 1 e m --15 J N El June 20, 1944- A. E. JOEL, .iR

TELEPHONE SYSTEM Filed July so, 194s 4 sheets-sheet 3 MNM.

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TELEPHONE SYSTEM Filed Ju'ly so, 194s 4 sheets-sheet 4 Fla. 4

` /A/vE/vro@ A. 2 JOEL, JR

WMWW

Patented June 20, 1944 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Amos E. Joel, Jr., New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 30, 1943', Serial No. 496,739

Claims.

This invention relates to automatic switching telephone systemsand more particularly to the control of pulse responsive devices for such systems.

Itv is the object of the invention to increase the range of operation of impulse systems for controlling the operation of switches in automatic switching telephone offices.

Revertive impulse systems have been used in both panel and cross bar automatic switching telephone oices in which a fundamental circuit is used for controlling the positioning of switches. In well-known systems of this character a group of counting relays and a stepping relay are used for controlling the number of pulses which comprise a digit, the connection to the counting relay being automatically altered for each digit by a steering device. The fundamental circuit of these systems extends from battery through the Winding of a line relay, known as the L relay, thence over one leg of the fundamental circuit loop through the winding of the above-mentioned stepping relay and a contact of the last operated counting relay, over the other leg of the fundamental circuit through the winding of another stepping relay to ground in a nearby switch controlling device. When the fundamental circuit is closed both stepping relays are operated and released by the closed circuit and shunt method a number of times for each digit depending upon the counting relay connection to the originating pulse controlling device. The L relay remains operated during the pulsing of a digit and is released during the interdigital period. This invention contemplates the use of such fundamental circuits in automatic switching offices a considerable distance apart for setting the switches in one cnice according to the digit pulse controlling devices of the originating oflice.

A feature of the invention consists in the use of the revertive pulsing fundamental circuits in two automatic switching telephone offices, one originating and the other terminating, interconnected by a composite signaling circuit and associated devices for controlling the setting of switches in the distant terminating oflice.

Another and related feature consists in connecting the digit pulse controlling mechanism of the originating office sender fundamental circuit with the mechanism of a composite signaling outgoing trunk circuit, the fundamental circuit thus extending from the originating sender through the mechanism of the composite signaling outgoing trunk circuit and in connecting the oiilce fundamental circuit with the mechanism of a composite signaling incoming trunk circuit in said terminating office, thus extending this second fundamental circuitfromthe terminating ofiice'through` the mechanism ofthe composite signaling incoming trunk circuit for simultaneously actuating the mechanism of both fundamental circuits under the control of the originating oflice sender.

Another and related feature consists in the use of a telephone operatorsposition mechanism of the originating oflice for controlling the mechanism of the fundamental circuit extending between the terminating office and the incoming ycomposite signaling trunk circuit to complete an automatic switching telephone connection be- ,tweenl the originating office operators position and a subscriber or operator in the terminating cnice.

These and other features will be discussed more fully in the following description when taken in connection with the illustrated embodiment in which:

Figs. l, 2 and 4 illustrate the originating mechanism of one automatic switching telephone office and Fig. 3 the terminating mechanism of another automatic switching telephone oflice. The gures taken separately illustrate the followmg:

Fig. 1, a subscribers line, a register sender and the switches which are operated under the control of the sender.

Fig. 2, a composite signaling outgoing trunk circuit connected to a four-wire transmission line having speech amplifying repeaters therein.

Fig. 3, an incoming composite signaling circuit connected to the terminating end of the fourwire transmission line and connected to a sender and the switching mechanism ofthe terminating oilice.

Fig. 4, a telephone operators position.

The composite signaling relays are associated with the composite signaling trunk circuit, Fig. 2, in one oiiice and with the composite signaling trunk circuit, Fig. 3, in a distant oice for increasing the distance over which pulses may be transmitted for yconnections between two full mechanical switching ofces. As noted in the art of record, the one fundamental circuit is ordinarily used between the signal sending devices and the signal receiving devices. The arrangement shown herein has two fundamental circuits, one between the outgoing composite trunk, Fig. 2, and the sender |20 and another fundamental switch controlling mechanism of the terminating circuit between the incoming trunk, Fig. 3, and

tration, let it be assumed the sender circuit 330. Between these two trunk circuits the composite signaling circuit is used to develop in one fundamental the pulses, which are created in the other fundamental circuit. This composite signaling circuit is also used for transmitting signals from the distant end to the originating end for various purposes. The operation of the composite signaling circuit will first be discussed.

Referring to the composite signaling relays 220 and 320 each has two windings designated Sl and S2. The two signaling windings SI and S2 of each relay have approximately the same number of ampere turns and are connected diiierentially. One is connected to the composite signaling channel 264 and the other winding to a biasing potentiometer. The current builds up and decays in the two windings at the same rate. The other terminals of the two windings are connected together and tov a lead marked M. In the outgoing trunk Fig. 2, lead M eX- tends to the armature of the L relay 200 which when released is associated with ground and when actuated is connected to battery through the contact of relay 205 for the start signals and through the contact of relays 205 and 20| for the transmission of pulses. The M lead in the incoming trunk, Fig. 3, is connected through contact 5 of relay 308 to ground on Contact 4 of relay 309. Battery is connected to the M lead of the composite relay 320 either by the operation of relay 300 or by the operation of relay 3D1 and the operation ofrelay 308. The

circuit connections to the composite signaling relays 220 and 320 with the other relays normal as shown, causes both composite relays to remain released. The current ows from the biasing potentiometer through windings S| to ground connected to the M lead of each of the composite signaling relays 220 and 320. This biases the composite relays to their released positions. When the L relay 200 is operated battery is connected through contact I of relay 205 to the M lead of relay 220. This causes current to ilow in the SI winding of the composite relay 220 in the opposite direction and tends to operate this relay but current also ilows in the S2 winding of relay 220 tending to release the re-` lay and because the voltage at the biasing potentiometer is higher than ground,V the current through the S2 winding is enough greater than that through the SI winding to hold the relay 220 released. The'current ilowing through the S2 winding of relay 220 flows out over the composite signaling lead 264 and through the S2 winding of the composite relay 320 in the distant oice. Here, because of its greater value, the current in the S2 winding overpowers the effect of the current in the SI winding and operates relay 320. As later will `be explained, the operation of relay 320 establishes a circuit for the A relay 306 in the distant incoming trunk and other mechanism as shown. The duplex action of this signaling system may be illustrated by now referring toa signal transmitted `from the distance cnice, Fig.v 3, to the originating oiice, Figs. land 2 after the composite signaling relay 320 has been operated. For this illusthat the L relay 200 is operated and relay is released. Thus, battery is connected to the M lead 26| through the S2 winding of relays 220 and 320 to ground in the incoming trunk, Fig. 3. In order to transmit a signal from the incoming trunk, Fig. 3, battery may be connected to the M lead of composite signaling relay 320 as described. Battery connected to this M lead and battery connected to the M lead of composite signaling relay 220 places the S2 windings of both relays in series and no current will now through either one of the S2 windings. Relay 220 now operates from the current through its S| winding and relay 320 remains operated from the current through its Sl winding. The operating current in the SI winding of relay 320 takes the place of the previously operated current in the S2 winding. Thus, when signaling current is transmitted from Fig. 3 to Fig. 2 with the current as related in this example,V relay 320 remains operated in order to continue the circuit for the A relay 306 and establish a circuit for operating relay 220 to transmit a start pulsing signal, a signal to an operator or for other purposes such as releasing a sender at the termination of the transmission of digits.`

' A telephone call is initiated over the Wires of this system in the usual manner by a subscriber A which under some conditions may be a telephone operator. The removal of the telephone receiver at station A by a subscriber transmits a signal to a telephone oilice which in this instance is shown diagrammatically as a full mechanical switching office of the type disclosed by R. Raymond in his Patent 2,106,360, January 25, 1938. In response to the removal of the receiver, switches are energized in the full mechanical switching oce for connecting the subscribers line to a link |0| which selects an idle pulse responsive sender |20 and connects it to the calling line. The link |0| used for connecting the calling subscriber with a sender is shown diagrammatically as well as the pulse responsive mechanism, the registers, and sequence circuit of the sender |20. 'Ihe pulse responsive mechanism energizes the register setting mechanism 2| for setting a number of registers according to the dial pulses transmitted for connecting the calling subscriber with another subscriber. In this case, it may be assumed that the calling subscriber desires a connection with a subscriber connected with another full mechanical switching oiiice a considerable distance away which requires special signaling equipment to obviate the use of an intermediate switching oce for completing a connection to this distant subscriber. The code registers which are set by the calling subscriber A indicate the oice to which the call shall be extended and the sender |20 thus controls the selection of an outgoing trunk for this connection which outgoing trunk is shown in Fig. 2. The calling subscriber continues to dial the numerical digits which are also set up on the registers |22. These registers are associated with a steering circuit which successively associates the registers with the counting relays shown as the pulses are transmitted over a fundamental circuit extending through the sender mechanism including stepping relay l23, the contact of the last counting relay |50A and the pulsing mechanism of the outgoing trunk circuit Fig. 2.

The outgoing trunk, Fig. 2, is permanently connected with the incoming trunk, Fig. 3, of the distant oce and as soon as the sender |20 is ready to complete the telephone connection and the fundamental circuit has been established, the fundamental L relay 200 of Fig. 2 is energized. The circuit for the L relay 200 may be traced from battery through its upper winding, Contact of relay 203, left upper winding of hybrid 201,

`aesinet winding of stepping relay |23, contact of countingrelay |59A, .left lower winding of hybrid .201, contact 2 of. relay 203, contact l of relay 204 to ground on contact 3 of relay 205. The L relay 200 and the stepping relay |23 operate in the circuit traced. The operation of the L relay 200 connects battery through contact of relay 205, contact of relay 200, lead 26|, lower winding of composite signaling relay 220, composite signaling lead 264, lower winding of composite signaling relay 320, contact of relay 308 to ground on contact 4 of relay 309. For reasons given herein, the composite signaling relay 220 does not operate when the above 'circuit is established. The composite signaling relay 320 is operated in the circuit traced which connects ground to the winding of the A relay 306 to battery operating this A relay. The operation of. relay 306 establishes a circuit `for relay 301 from battery through the winding of `relay 301, contact 2 of relay 308, contact 3 of relay 309 to ground on contact 4 of relay 306. Relay 306 also establishes connections for the fundamental pulsing circuit between the incoming trunks Fig. 3 and the sender 330 by first connecting a potentiometer, comprising resistance 3|| to ground and resistance 3l0 to battery, through contact 4 of r-elay 304, winding of polarizing relay 305, contact 5 of relay 304 through a standard incoming trunk of this distant oice to an incoming junctor circuit. This causes the energization of link 325 shown diagrammatically, which selectsv and associates a sender with the tip and ring `conductors extending through the regular incoming trunk to the composite signaling trunk. The potentiometer associated with relay 306 is this connected through the link to the stepping relay 333 of a Sender such as sender 330. The mechanism of the distant oiiice, including sender 330 in the right portion of Fig. 3, is diagrammatically shown and with the exception of the composite signaling trunk may be substantially the same as shown in Patent 2,089,921, issued to W. W. Carpenter, August l0, 1937.

The fundamental circuit shown for the sender in this distance office and the registering mechanism maybe the same as shown in the abovementioned patent to Carpenter. In place of the more complicated mechanism ci this patent, relay 334 has been shown for connecting the registering mechanism with the pulse responsive relay 332 connected with the fundamental circuit.

The stepping relay 333 operates when connected to the potentiometer over the circuit traced and the operation of the stepping relay establishes an obvious circuit for relay 332 and the latter relay establishes an obvious circuit for the L relay 33 The ground connected through the winding oi the` L relay 33| also extends to the tip conductor 340, contact of relay 304, Contact 3 of the A relay 306, contact 2 oi relay 301, winding of relay 303 to battery operating relay 308. Relay 308 in operating locks through its contact 3 to ground on contact 4 of relay 304 completing the fundamental circuit between the incoming trunk and the sender 330. The L relay 33| is now held operated oVer one leg of the fundamental by way of the tip conductor 340, contact l of relay 304, contact 3 of the A relay 306 which is slow to release and remains operated during the pulses for each digit, contacts 4 and 3 of relay 308, contact 4 oi relay 304 to ground. lThe stepping relay 333 is held operated over the other leg oi the fundamental by way of ring conductor 34|, contact 6 of relay 304, winding of polarized relay 305, contact 5 of relay 304, contacts 6 and 5 of relay 306 to the aforementioned potentiometer. Relay 308 also opens the-operating vcircuit for relay 301;

the latter relay is, however, slow in releasing. After relay 308 has operated and before relay 301 has released, a -s'tart 4pulsing signal is established to the distanct office which operates the composite 'signaling relay v220 for "automatically starting the ygeneration of pulses over the fundamental circuit between the originating sender A|20 vand the 4outgoing trunk` circuit,.Fig. The

vcircuit operating relay 220 Amay be traced from battery through contact of relay 301, contact 5 of relay 30'8, M conductor 35|, S2 winding of composite signaling relay 320, S2 winding` of composite signaling relay 220, 'M lead 26|, Contact oiL relay200 to battery on contact 2 of relay20l.

Relay '220 is now operated-from current through its .SI winding and relay `32|) remains operated from current through its SI winding since the `circuit above traced neutralizes'the S2 windings -damental circuit was established to direct ground on contact 3 of relay 205.` The release of relay 301 shortly after the operation of relay 308 opens the battery circuit from the incoming trunk `through winding S2 lof the composite signaling relay 220 causing the release of the latter relay. The operating circuit for relay 320 now extends from battery through contact of pulsing relay 20|, contact of relay 205, contact of L relay y200, M lead 26|, S2 windings of relays 220 and 320, contact 5 of relay 308, contact I of relay 301, `contact 4 of relay 306 to ground.

During the momentary operation of relay 220 which caused the operation of relay 205, a shunt is placed across the winding of relay 206 so that the latter relay does not operate, but upon the release of relay 220 battery flows through the winding of relay 205, winding of relay 206, contact 2 of relay 205 to'sleeve ground connected to conductor 262 which locks both relays 205 and 206 to the sleeve ground. Other signals from the distant ofce which thereafter operate the composite signalin'g relay 220'wi1l cause the operation of reversing relay 203 for purposes explained later. The start pulsing signal returned to the outgoing trunk circuitFig. 2, therefore, establishes the pulse generating circuit in the originating funda- I mental circuit and arranges a normal composite signaling path between the distant'oflice and the originating oflice for use after` the digits have been transmitted and before if trouble is encountered. A

Pulses are now generated by the operation of the pulsing mechanism in the originating or rst fundamental circuit causing responsive action in l the terminating or second fundamental circuit. Thel operation of the stepping relay 220 establishes an obvious circuit for relay 20| Relay 2| is slow to operate and does not operate at this time. Relay 20| in operating opens the composite signaling battery and connects ground through contact I of relay y205 and the contact of the L relay 200, S2 winding of relay 220,.signaling circuit .2.64, S2 winding of relay 320 to ground, causing the release of relay 320,` which associates a shunt' ground With the ring conductor .34| to cause therelease of stepping relay 333 in thedistant fundamental circuit. 'I'he operation of relay also connects ground through contact 2 of relay 204, lower winding of L relay 200, contact 3 of relay 204, through the winding of the L relay 200 to battery for holding this relay operated and through contact I of relay 203, thence over the tip conductor 228 of the fundamental circuit which causes a shunt to be placed on both stepping relay 202 of the trunk circuit and stepping relay |23 in sender I 20 causing their release. The contact of the stepping relay |23 is connected through a particular register to one of the counting relays depending upon the original setting of this register by pulses from the calling subscriber. Assuming that this particular register associates the contact of stepping relay |23 with theV lead |36, the counting relay |56B is energized by the first operation of relay |23 and relay |56A is operated when the stepping relay |23 releases. The circuit for the counting relays is clear since with relay |23 operated a circuit is established for relay |56B to battery and also relay |56A isA shunted, but when relay |23 is released a circuit is established from battery through the winding of relay |56B, winding of relay |56A, contact of relay |56B to ground.

In the distant office the release of composite signaling relay 320 connects ground through contact 6 of relay 306, contact 5 of relay 304, winding of polarizing relay 305, contact 6 of relay 304, thence over the ring conductor 34| to the winding terminal of the stepping relay 333, thus shunting the stepping relay to cause its release. 'Ihe release of relay 333 releases relay 332 which opens the circuit connection to the registering mechanism in the usual manner and disconnects ground from the L relay and the tip conductor 340 of the trunk. The distant oflice L relay 33| is'however maintained operated from battery through its winding over a circuit to tip conductor 3140, contact of relay 304, contact 3 of relay-306, contacts 4 and 3 of relay 308 to ground on contact 4 oi' relay 304. The L relay 33| is thus held operated during the pulses transmitted for registering a digit. l 4 The release -of stepping relay 202 causes the release of relay 20| and thus the stepping relays 202 and |23 again operate. Each operation and release of the stepping relay 202 transmits a signal over the composite signaling circuit to cause the pulsing relays of the fundamental circuit extending between sender 330 and the incoming trunk, Fig. 3, to function and atthe same time causes the stepping relay fundamental to function. y RelayV |23 successively operates the pairs of counting relaysinthe manner described until the end'counting relay |59A operates to open the fundamental circuit extending between sender |20 and the outgoing trunk circuit, Fig. 2. This terminates the pulses for the rst digit and causes the mechanism of sender |20 to functionduiing the interdigital period for connecting the next set of registers to the counting relay circuit for the next digit to be transmitted. |Also during this interdigital period the registering mechanism in sender 330 is operated for causing the rst digit to be registered. When the fundamental circuit between sender |20 and the outgoing trunk,lFig. 2, is opened, relay 200 is released and relays 20|l and 202 are released. With relay200 released battery is disconnected from and ground is lconnected tothe M lead of the composite signaling vrelay 220, thus causing the release of the composite signaling relay 320 |23 in the originating which opens the holding circuit for the A relay 306. Release of relay 306 releases the L relay 33| Ain the distant sender causing the registering mechanism shown diagrammatcally as 335 to function.

When the sender |20 has released the counting relays and the steering circuit |22 has connected the next register with the counting relays and closed the fundamental circuit, stepping relays 202 and |23 are again operated and the L relay 200 is operated as previously described since relay 205 remained locked to the sleeve conductor 262. During the interdigital period a circuit is established for the slow operating relay 2|| from battery through resistance 2|2, winding of relay 2| I, contact 4 of relay 205, contact 2 of relay 20| to ground which operates relay 2|| to open the operating circuit for relay 20|. The stepping relay 202 in reoperating places a ground shunt around the winding of relay 2|! but this relay is slow to release to permit a signal to be transmitted over the composite signaling circuit. The operation of the L relay 200 connects battery from the back contact of relay 20|, contact of relay 205, contact of relay 200 to the M lead of the composite signaling relay 220, thence through the S2 winding of this relay and the S2 winding of composite signaling relay 320, contact 5 of relay 308, contact of relay 301 to ground on contact l of relay 309, thus causing the reoperation of the composite signaling relay 320 which reestablishes a circuit for the A relay 306 preparing the fundamental circuit between the incoming trunk circuit, Fig. 3, and the sender 330 as was originally described. The release of relay 2H again establishes the circuit for relay 20| from groundl on the stepping relay, back contact of relay 2H, winding of relay 20| to battery. Pulses are now generated for the second digit which causes the release and operation of the composite signaling relay 320 for registering the digit in sender 330 and for causing the operation of the counting relays according to the connection of the second register with these counting relays. As previously described, each operation of relay 20| connects a ground shunt to the tip of the line causing the release of stepping relay |23 and stepping relay 202 and also causing the release of the composite signaling relay 320. The release of relay 202 as is apparent causes the release of relay 20| and the stepping relays and composite signaling relays 320 and pulses are transmitted until such time as the incoming relay |59A again opens the fundamental circuit to terminate the pulses for the second digit. This results in an interdigital period, releases L relay 200 and L relay 33| in both fundamental circuits causing the registration of the second digit in the sender 330. The steering circuitl of sender |20 now connects the third set of registers with the counting relays and releases the counting relays to again establish the fundamental circuit between the sender S20 and the outgoing trunk circuit. The operation for transmitting the pulses for the third digit and subsequent digits is the same as has already been described.

As shown in the aforementioned Patent 2,106,360 to R. Raymond the fundamental circuit is again closed in the originating sender |20 after the last digit. This signals the terminating sender 330 that the last digit has been sent out. The closure of the fundamental again operates the L relay 200 which connects battery from contact of relay 20|, contact 3 of relay 205through the contact of L relay 260 to the M lead of the cornposite signaling `relay 2,20. The circuit extends through the S2 windings of relays 220 and 320 to ground on contact 4 of relay 309 energizing the composite signaling relay 320 which again operates the A relay 306. It will be remembered that after each digithas been sent out relays 32o and 306 are released. This procedure is the same after the last digit has been dialed as well as after other digits.

In the terminating sender, the fundamental is again closed by the operation of the A relay 306 the same as previously described. Since the last digit has been registered by sender 330, this sender in recognition of `the registration of the last digit now establishes a circuit for a reversing relay in the manner fully described in the aforementioned Patent 2,089,921 to W. W. Carp-enter. Relay 336 diagrammatically shows the relay for transmitting the reverse pulse and is operated when the fundamental between the incoming trunk in Fig. 3 and sender 330 is closed after the last digit has been transmitted. A diagrammatic illustration of this arrangement shows the operation of relay 332 and 33| establishing a circuit for relay 33,4 and a circuit from ground through the contact of relay 3,34 and through the registering mechanism for operating the relay 336 to transmit the reverse battery pulse. The operation of the latter relay connects battery to ring conductor 34| which extends through contact 6 .of relay 304, winding of polarized relay 305, contact of relay 304 to the potentiometer associated with contacts 5 and 6 of relay 306. The current is now in thel proper direction for operating polarized relay 305 which establishes a circuit from ground through contact of relay 3,06, contact of relay 305 winding of relay 309 to battery. Relay 30,9 in operating locks to ground on contact of relay S and immediately transmits the signal to the originating sender |20. For this signal, battery is connected through contact 4 of relay 309, contact of relay 301, contact 5 of relay 308, M lead 35|, S2 windings of composite signaling relays 320 and 220, contact of relay 200, contact 3 of relay 205, to battery or ground on contact of relay 20|. Under normal circuit conditions the signal is retained before relay 20| is operated.

As previously described, the connection from battery to battery through the S2 windings of the composite signaling relays 32,0 and 220 neutralizes these windings and the current through the SI windings is made effective. This current through the SI winding holds relay 320 operated and operates relay 220. The operation of relay 220 establishing a circuit for the reversing relay 203 from ground through the contact of relay 220, jack 2|1, contact of relay 206, winding of relay 203 to battery. The operation of relay 203 reverses the current flow in the fundamental circuit and establishes an operating circuit ithrough its contact 3 for relay 204. Relay 204 locks to ground ove-r the sleeve circuit 2,62 opening the circuit for the stepping relay 202. Battery is thus connected through yrthe winding of L relay 200, contact 2 of relay 203, lower winding of hybrid coil 201, thence over the fundamental circuit through the winding of relay |23, winding of polarized relay |24, upper winding of hybrid coil 201, -contact of relay 203, contact 3 of relay 204, lower winding of L relay 200, contact 4 of relay .204 to ground.

The current in the circuit traced through-the winding of polarized relay |24 is in the direction to operatel this relay and the operation of relay |24 establishes4 areleasing circuit for sender |20. The sender |20 and link |0| are now disconnected from the line and trunk conductors. The relay 200 releases causing the release of the distant composite relay 320, the release of the A relay 306. The release of relay 306 establishes, a circuit from ground on `its contact 4 through contact I of relay-300 winding of relay 304 tobattery operating the latter relay. The operation of relay 304 connects thel tip and ring leads through its contacts kand 6 tothe distant oiilce, thus closing the transmission circuit. Ihe L relay 200 is connected over the line loopthrough the, subscriber station and reoperaites. A-circuit is thus established for relay 320 which reoperates relay 306. The operation of relay 306 with relay 304 oper-ated establishes a locking circuit for relay 304 and; opens the locking circuitv for relay 303 which releases. The release of relay 308 opens the locking circuit for relay 300whi1ch releases. Release of relay 300 removes battery from the M lead of the composite signaling circuit which causes :the release of the composite signaling relay 220. Releasev of relay 220 releases relay 203. Since relay 204 is locked to the sleeve circuit 262, the circuit is now established placing condenser 2|5 across the transmission coils of the hybrid coil 201. This circuit may be traced from the tip conductor through the upper winding of hybrid coil 201, condenser 2|5, contact 2 of relay 204, over coil of hybrid 201, ring conductor 221 and through other mechanism of the transmission circuit. Relay 304 when operated also connects the winding of relay 305 to trunk conductors 340 and 34| so that a reverse battery signal may be sent upon the termination of the connection.

The sender 330 having had its registers seit in accordance with digit pulses indicating the wanted subscriber, now operates the switchingmechanism for connecting the called subscriber A with the calling subscriber B. A four-wire transmission line has been shown, which is well understood in the art, using hybrid coil 201 and 330 having balancing networks 209 and 302 regulated according to the lines With which they are associated. The repeaters in the four-Wire line are shown diagrammatically to indicate that the iiow of voice currents over conductors 235 and 236 is in the right-hand direction and the ow of voice currents in the lower channel comprising the two wires 231 and 23,8 is in lthe left-hand direction through repeaters 303 and 2|0. Thus the conversation from .subscriber A is transmitted over the upper channel of the four-wire circuit comprising repeaters 208 and 30| and the transmission from subscriber B to subscriber A is over the lower channel of the -four-wire circuilt through repeaters 303 and 2|0. With relay 305 connected to conductors 340 and 34| asset forth in the foregoing, signals may be transmitted by reversing the battery and ground in this dial out oiiice to operate relay 305 `to `charge for the office and o iiice calls and for disconnecting purposes. Relay 30.5 establishes a circuit for relay 309V which operates and connects battery to the M lead 35| which operates the composite signaling relay 220 as herein described. It will be remembered that relay 206 is locked to the sleeve-ground over lead 262 and therefore the operation of relay 220 establishes a circuit -for the reverse battery relay 203. This reversal of battery and ground over trunk leads 221 and 228 is employed for operating the charging mechanism associated with the calling line in any well-known manner,

' An operators'position circuit-is shown in Fig.4 having a 'telephone set arranged for listening and talking in the manner disclosed in Patent 2,294,237 to J. B. McKim, August 25. 1942. This telephone circuit is normally arranged for monitoring over the yfour-wire circuit and by the-operation of'relay 424 is arranged for talking to either subscriber and listening to subscribers conversation. This telephone circuit is arranged With a combination of hybrid coil windings in such manner that voice transmission will not extendY through the telephone circuit from one fourwire channel tothe other and thus obviates voice echoes as'fully described in the aforementioned patent to McKim. Since this telephone circuit is fully described inthe patent, it is believed unnecessary to encumber this description with a description of'fthedirection of transmission current Vflowy through the, various windings of the telephone circuit.

The operators position circuit, Fig. 4, is arranged so that this operator may cause the mechanism'of this incoming trunk and sender in the distant office to function Yby pulsing over the composite signaling circuit by the use of dial 400. This operator selects anidle trunk circuit and inserts plug 2|6 into jack 2|1 which disconnects the composite signaling circuit from the trunk of Fig. 2 at the same time it is connected to the operators position. Key 406 is operated to establish the circuit between the operators position and the distant oiiice. The operation of key 406 establishes an obvious circuit for operating relay 405. The operation of relay 405 connects battery through the contact of relay 402, contact I of relay 404, contact of relay 405, contact 3 of key 406, plug 2|6 and jack 2|1 to the M lead 26|, thence through the S2 windings of the composite relays 220 and 320, contact of relay 308, to ground on contact 4 of relay 309. This operation Was previously described upon the initiation of the call from subscriber A which energized sender to transmit this signal over the composite signaling circuit. Thus the composite signal relay 320 is energized which energizes the A relay 306. The energization of relay 306 vassociates the potentiometer connected With contacts 5 and 6 through the winding of polarized relay 305 over the ring conductor, winding of stepping relay 333 to ground. As previously described, the operation of the stepping relay establishes the circuit for relay 332 which connects ground through the winding of the L relay to battery and also connects ground over the tip lead to contact of relay 304, contact 3 of relay 306, contact 2 of relay 301, Winding of relay 308 to battery. Relay 301, as previously explained, is operated from battery through its winding, contact 2 of relay 303, Contact 3 of relay 309 to ground on contact 4 of relay 306. Relay 300 in operating establishes a locking circuit for the Lrrelay 33| from ground on contact 4 of relay 304, contacts 3 and 4 of relay 308, contact 3 of relay 306, thence over tip lead through the winding of the L relay 33| to battery. Relay V308 also opens the circuit for relay 301 but relay 301 is slow to release and before it releases a signal is transmitted to the operators position. VBattery through contact I of relay`301 and'contact 5 of relay 308 is connected to M lead through the S2 windings of composite signaling relays 320 and 220 to battery on the contact of relay 402 as previously traced. Battery to battery, through the S2 windings of composite signaling relays, neutralizes through its Sl winding, also relay 220 is operated through its Sl winding. The operation of relay 220 connects ground through the contact of jack 2|1 and plug 2|6, Contact 2 of key 406, winding of relay 403 to battery operating the 403 relay which lights lamp 408. The lighting of lamp 408 is a signal to the operator that a sender, such as sender 330, has been selected in the distant oice and is prepared to receive pulses. Relay 403 in operating establishes a locking circuit for itself through contact 3 of relay 40| which holds the lamp lighted until the operator starts to dial. The operator may now dial according to the connection desired. Y

The movement of the dial from its normal position to the nger stop operates relay 40| by the connection of contacts 2 and 3 associating ground through the winding of relay 40| to battery. The operation of relay 40| opens the locking circuit for relay 403 causing it to release and extinguish the signal lamp 408. Relay 40| in operating also establishes a locking circuit for itself through its contact contact of relay 405 to ground. Upon the return of the dial to its normal position contacts 4 and 5 are intermittently opened and closed. The stepping relay 402 is shunted when contacts 4 and 5 are closed by the ground connection 4|| but when the contacts 4 and 5 are open, relay 402 is operated from ground 4|| through its winding, resistance 401 to battery. Thus relay 402 is intermittently operated a number of times depending upon the nger grip used by the operator in moving the dial from its normal position. The intermittent operations of relay 402 intermittently associate battery and ground through contact of relay 404, contact 2 of relay 405, contact 3 of key 406, plug 2|6 and jack 2| 1, thence over the M lead and the S2 windings of composite signaling relays 220 and 320. This intermittently operates and releases the composite signal relay 320 which causes these windings and relay 320 is held operated 75 the pulsing mechanism of, sender 330 to operate and release responsive to each pulse of the dial as previously explained in connection with the pulsing mechanism of the fundamental circuit of Figs. 1 and 2. `When the dial restores to its normal position an interdigital period takes place permitting the registration of the digit by the registers 335 in sender 330.` Thisinterdigital period is brought about by the operation of relay 404 from battery through its winding, contact 2 of relay 40|, contacts and 2 of the dial 400 to ground. Relay 404 in operating disconnects battery through its contact which extends over the composite signaling` circuit Vand causes the release of composite signaling relay 320, and the A relay 306. The release ofthe A relay/e306 releases the L relay 33| which brings about' the interdigital period in the senderr330. Thejijeoperation of the dial causes the release of lrelayr4l34 when the dial is moved away from its normal position thus again closing the circuit for the composite signaling relay 320 to reoperatefthevv Arelay 306 and upon the returnmovement ofthe dial, contacts 'land 5 are again intermittently opened and closed for causing the steppingrelay 402 to intermittently operate and releaseyjthe composite signaling' relay 320 to causathe ,second digit to be recorded inthe `sender 330'. pon the return of the'dial 400 to its normal position, relay 320 is again released to effect the interdigital period required for the registration of the digit in the sender 33u, Qgzf It will be recognized that upon the it'ernunai tion of the transmission'of digits, relay 404 r'eacci-,th

mains operated andtherefore the operator depresses key4|2 in order to signal the distant sender thatfthe last digit has been transmitted. This signal again operates the composite signaling relay 320 which again operates the A relay B. As previously described, sender 330 is adjusted after the last digit has been received so that the transmission of the pulse from the originating end operates a battery reversing relay such as relay 336, The operation of relay 336 returns the reverse battery pulse which operates the-polarized relay 305 and relay 305 establishes acircuit for relay 309.' The operation of' relay 309 `now establishes battery circuit between the trunk of Fig. 3 and the operators position by connecting battery through its contact 4 to the M lead which as previously explained operates the composite signaling relay 220 by neutralizing the S2 windings of both composite signaling relays. a connects ground through its Contact, jackZl'l', plug 2|5, contact 2 of key 406, winding` of relay 403 to battery, to reoperate relay 403 and light lamp 403 indicating to the operator that the distant sender 330 has respondedto the digit pulses and has completed its registrations. Relay 309 in operating establishes a locking circuit for itself to ground on contact I of relay 308. Relay 403 in operating locks to ground on contact 2 of relay 404 since it will be remembered that the latter relay is operated when the dial 400 restores to its normal position after each digit has been dialed. Upon observingthe lamp 408, the operator momentarily restores key 4I2 to normal, disconnecting battery from the composite signaling path. The composite signaling relay 320 and the A relay 306 Vrestore to normal which establish a circuit for relay 304 from ground on contact 4 of relay 303, contact I of relay 309, winding of relay 3'04 to battery. The operator again actuates key M2 to reestablish the circuit for relays 320 and 306. Relay 304 now locks to ground on contact '4 of relay 306.` Relay 308 remains locked through contact l of relay 304 to ground on contact of relay 306, and thus relay 309 remains locked to ground on contact I of relay 308 until after the operation of relay 306 when both relays 300 and30'9 release. The operation of relay 304 associates the operators telephone circuit` through the switching mechanism 339 of the' distantswitching oiiicel with a subscriber or a telephone operator B which has been connected thereto by sender 330 in accordance with the settings of registers 335. The operation of 'relays 304 and`300 connects the polarizedrelay 305 to the tip and ring conductors 340 and 34| for revision battery supervision. The operator may have other types of mechanism forassociating The operation of the latter relay the telephone set with the transmission circuit.

The operator may now restore key 406 to normal which restores the relays of the pulsing circuit and keep key ,412 operated for supervisory signaling purposes. Y i, l l

.The operatorsposition, as above described, hasv essentiallyVv a fundamental circuit therein comprising the'stepping relay and dial contacts along with relays .for associating this signal responsive mechanism with the composite signaling circuit for responsive action of the pulsing mechanism in the fundamental of a distant ofiice. A distant subscriber may be reached from a subscriber entering sender |20 in an oiiice using a fundamental circuit between the sender circuit and the trunk circuit of Fig. 2 or from the operators position using fundamental as described which'materi'ally decreases the 'mechanism for automatic switching systems inwhich` revertive pulses are employed and decreases the 'number of such switching `offices required to complete connectionswhich couldunder other circumstances be considered as toll connectionsj It is" recognized that the sender |20 by selecting an outgoing trunk connected directly to a nearbyv auto'- matic switching oiiice would-operate in themanner disclosed in the aforementioned patent to Raymond. In this type of 'connection a single fundamental circuit is used which would substantially comprise Athe connection of "the counting relays and steppingfrelay of sender |20 with the L relay and stepping relay of sender :330.

What is claimedis:

1. In a telephone'switching system, a first automatic switching v -office havingregister senders arranged forrevertive-pulsingover a fundamental circuit, a second lautomatic switching oilice having register senders arranged 'for vrevertive pulsing over "a fundamental circuit, outgoing trunk circuits in saidvrst ofiicejincoming trunk circuits in said second oiice a speechtrans'mission' circuit and a composite signaling circuit extending between said outgoing and said incoming trunk circuits, means for connecting one of said outgoingtrunks'with a sender in saidiirst cnice and the associated incoming trunk with a sender in said' second office, means in said trunk circuits for forming revertive pulse fundamental circuits with the senders `associated therewith thus formingv separate revertive pulse fundamental circuits in each oirice, means for closing i the fundamental circuits of both lofce's by the transmission of signals over said composite signaling circuit, and means including said composite signaling` circuit -for operating the mechanism of both fundamental circuits simultaneously according to digit registrations in the sender of said first office for completing an automatic 'switching telephone connection in said second office. 2.`In `a telephone switching system, a v'rst automatic Switching `oilice havingregister send- 'ers arranged for revertive pulsing over a fundamentatcircuit, a second automatic switching office: having register senders arranged for revertive pulsing over a fundamental circuit, outgoing trunk circuits in said first oflice,"incoming trunk circuits in said second cnice, a speech transmission circuit and a composite signaling circuit extending between said outgoing and said incoming trunk circuits, means for connecting one of said outgoing trunks with a sender in said 'first office and the associated incoming trunk with a sender in said second oce, Vmeans in said trunk circuits for forming revertive pulse fundamental circuits with the 'senders' associated therewith thus forming separate revertive pulse fundamental circuits in each oiilce, means for closing the fundamental circuits of both ofiices bythe transmission of signals over said composite signaling circuit, means including said composite'sig'naling circuit'ior operating the mechanism `of both'fundamental circuits simultaneously for registering digits in the sender of said second office for completing a telephone connection according to the called subscribers number registered in said first oflice, and means in said second sender for causing a signal to be transmitted over said composite signaling circuit upon the completion of registrations for dismissing the sender in the first office and for establishing said speech transmission circuit.

= a telephone. switching system, va jrst autQrnaticI switching cnice having register send-y ersarranged for revertive pulse control over a fundamental circuit,a second automatic switching Qflice havingl registerfsenders arranged for revertive pulse control-over a fundamental circuit, outgoing .trunk circuits in said i'lrst oiiice, incoming trunk circuits inV said secondY office, each-outgoing trunk circuit -v being'connected to an incoming trunk by a speech transmission circuit and a` composite signaling circuit, lines, means responsive Vto .a callover aline incoming to said first oiiice for` selecting a sender, means in said sender responsive todialpulses over said line for .registering-a call for said second .ofiice and for selecting an outgoing trunk, means in said sender and theoutgoing` trunk responsive to its A,selection for .transmittingwa signal pulse overl thecompcsite signaling, circuit from said rstofce to theincoming trunk in said second ofiicemcausing r`the selection of asender in said second office, ,means in saidsecond office for establish'ing 'A a revertive pulse Vfundamental circuit between the selectedsender of Said second office and saidincoming trunk circuit which, in being established.transmitsv ,a signal pulse over said composite signaling circuit .to ysaid rst office, means in said iirst oince responsive to said latter'signalpulse for .closing a Arevertive pulse fundamental'. circuit between the sender of said first cnice and said outgoing trunk circuit, and means responsive tothe establishing of both said fundamental circuits for registering digit pulses in said second oiiice sender under `the control of the mechanismA of said rst oice sender revertive pulse fundamental circuit, the responsive action of said composite signaling circuit and the mechanism of 'said second oilice sender revertive pulse fundamental circuit for completing the automatic switching telephone connection registered in said rst office sender.

4. In a telephone switching system, a iirst Y automaticl switching oilice having register senders arranged vfor revertive pulse control over a fundamental circuit, a second automatic switching oiiice having register senders arranged for revertive pulse control overa fundamental circuit, outgoing trunk circuitsin said rst oflice, incoming trunk circuits in said second oice, each routgoing trunk circuit being connected toy an incoming trunk by a speech, transmission circuit and a; composite signaling circuit, lines, means responsive to a call over a line incoming tosaid iirst ofiice for selecting a sender, means in said sender responsive to dial pulses over said line for registering a call for said second office and for selecting an outgoiong trunk, means in said senderV and the outgoing trunk responsive to its selection, for transmitting a signal pulse over the composite Asignaling circuit from said lrst office to the incoming trunk insaid second oiiice causingthe selection of 4 a sender in said second .oiliceVmeans in said second office for establishing av revertive pulse fundamental circuit between the selected sender of said second oiiice and said incoming trunk circuit which in being established. transmits a lsignalpulse over said composite signaling circuit to said first oifice, means in said first' oilice responsive to said latter signal pulse foriclosing a revertive pulse fundamental circuit between the sender of said first oince and f said outgoing trunk circuit, means responsive to the establishing of both said fundamental circuits for registering digit pulses in said second office sender under the control of the'mechanism of said rst oilice sender revertive pulse fundamental circuit, the responsive action of said composite signaling circuit and the mechanism of said second cnice sender revertive pulse fundamental circuit for completing the automatic switching telephone connection registered in said rst oiiice sender, and means in said second oiTice for transmitting a signal to said first office over said composite signaling circuit for dismissing the sender of the first office and for establishing said telephone transmission circuit after the last digit has been registered by said second ofiice sender.

5. 4In av telephone switching system, a rst automatic switching office arranged for revertive pulsing over a fundamental circuit, a second automatic switching oice having register senders arranged for revertive pulse control over a fundamental circuit, outgoing trunk circuits in said rst ofce, incoming trunk circuits in said second office, a speech transmission circuit and a composite signaling circuit extending between Vsaid outgoing and said incoming trunk circuits,

anoperators position in said first oiiice, means for connecting the mechanism of said position with said speech transmission circuit and the signaling circuit in an idle outgoing trunk circuit, means in said position circuit responsiverto its connection with said outgoing trunk circuit signaling means for sending a signal pulse to said 'second cnice incoming trunk circuit, means in said incoming trunk actuated by said signal pulse for causing the selection of a sender in said second cnice and the establishing of a revertive pulse fundamental circuit between said sender and said incoming trunk circuit, means responsive to the establishing of said fundamental circuit for causing a signal pulse to be transmitted from said incoming trunk over said composite signal circuit'to said voperators position, a signal in said operators position actuated by saidsignal rpulse to indicate that -the sender in said second oice is ready to respond to the revertive pulsing mechanism in said fundamental circuit, pulse controlling mechanism in said operators position including a dial and a stepping relay for operating the mechanism of said composite signal circuit and the mechanism in -the fundamental circuit of said second oiiice, each operation of said dial controlling the pulses of a digit by simultaneously operating and releasing the stepping relay in the operators position and the stepping relay in said fundamental circuit the number of timing required for each digit to set the registers of the sender in said second office, an operators telephone set in said position, and means responsive to the setting of said registers for completing a telephone connection lfrom said operators telephone set over said speech transmission circuit according to the settings of said register. Y

AMOS E. JOEL, JR.v 

